Skiing is a popular winter recreational activity for many people. In addition to alpine skiing on the piste, there are a number of other different skiing types or techniques.
General social trends suggest that users are also striving toward individualization and active delineation when it comes to skiing. Equipment providers are responding with an appropriate market differentiation. As a result, former niches ski touring, so-called “freeriding” and “freestyle skiing” have developed into separate market segments.
A. Ski Touring
Ski touring describes a form of alpine skiing where the skier is looking not only for downhill runs remote from prepared pistes, but also for the climb for this purpose. While the pure ski tourist tries to do completely without ski lifts and only selects downhill runs that he or she has personally worked out beforehand, off-piste skiing, also referred to as “freeriding”, describes an alpine version in which the skier uses an upper terminus of a lift as the starting point for his or her tour. Both share in common the downhill run into unprepared terrain and, even if to a varying extent, the climb.
In order to enable this climb, ski tour and freeride bindings have a climbing function, which allows the heel to release from the automatic heel bracket that is locked for the downhill run, and lets the boot rotate in the area of the toes without resistance.
Two fundamentally different types or mechanisms exist in the area of alpine ski tour binding systems. One type involves so-called plate bindings, in which the entire boot is fastened to a plate or a frame, which in turn is rotatably mounted to the ski. The boot is fastened to the plate or frame with binding elements, which essentially resemble those used under alpine downhill conditions. The rear end of the plate or frame is locked to the ski for the downhill run. In the climbing mode, the rear end of the plate or frame is released, so that the heel of the ski boot can be lifted during a pivoting motion of the plate or frame. However, the plate or frame is rigid, as is the sole of the conventional tour ski boot, so that the foot cannot carry out a rolling movement.
Another alpine ski tour binding system was developed in its basic form already 30 years ago by the Dynafit company, and has in the meantime become broadly used. In this system, the front area of the boot has an insert, which provides a hole-like depression in the sole extension of the ski boot on both sides, into each of which a respective mandrel of the binding engages. As a result, the boot is mounted so that it can rotate around this mandrel relative to the ski. An automatic heel bracket can block this movement, thus allowing a downhill run in the alpine style. To this end, the corresponding boot has another insert in the heel section, into which two pins of the automatic heel bracket engage from behind, preventing the boot from moving both vertically and laterally.
While ski boots with a rigid sole are normally also used even with these frameless types of alpine ski tour bindings, this binding in principle allows the use of ski boots with a flexible sole, even though the sole must be prevented from bending during a downhill run, for example by means of a suitable support, so as to achieve a defined release behavior.
The ski touring boots with a rigid sole, which are the boots used almost exclusively in alpine ski touring, are well-suited for downhill runs, and for climbing in steep terrain, which physiologically resembles “stair stepping”, in which the foot rolls only slightly if at all. When striding over an even or slightly inclined terrain, however, a physiological gait would involve a rolling of the foot, which is prevented by the rigid tour ski boots.
B. Telemark Technique
Telemark technique describes a form of skiing in which the heel is not fixed in place on the ski at any time. Historically, alpine skiing has developed from telemark-downhill skiing. Since in the Telemark downhill skiing, a turn is initiated as the result of angular momentum generated by a step change, before the curve is traversed during the lunge, the downhill run is characterized by its Telemark-typical step posture. Herein, the heel of the front outermost foot relative to the curve is fixed in place on the ski during the turn, similarly to the alpine style, while the heel of the innermost foot relative to the curve lifts up to realize a step posture, during which the knee and hip joint are bent, the knee gets closer to the ski, and the ski innermost to the curve is pushed relatively toward the back. As opposed to alpine downhill ski runs and alpine ski touring downhill runs, only the forefoot is rigidly joined with the ski during Telemark downhill runs, while the heel can be lifted from the ski against a resistance that grows as the knee increasingly bends.
Contrary to the climbing function of a ski tour or freeride binding, the forefoot in Telemark bindings is not fixed in place in a translational manner by a hinge, but the boot tip is instead clamped in torque-proof to enable optimal control of the ski. The front boot portion bends to allow the heel to lift, primarily by way of a kink fold provided therein. The ski is controlled by the ball of the foot, which then remains close to the ski even with the heel lifted due to the flexibility of the boot.
When the heel is lifted from the ski and the knee gets closer to the ski during a Telemark turn, this takes place against a resistance generated in part by the bending or “buckling” resistance of the boot, hereinafter also referred to as “boot bending resistance”, and in part by a binding bending resistance. As the heel lifts up, this movement is counteracted by the clamping of an often beak-shaped front sole extension into a receptacle (so-called “toe box”), so that the sole bends, and the kink fold area deforms, thereby generating the boot bending resistance. At the same time, however, a restoring torque is also generated by the binding as the heel lifts and the boot bends, which in conjunction with the torque resulting from the boot bending resistance makes it possible to exert pressure on the ski tip, i.e., to actively load the tips of the skis. The precise control of this load constitutes the basis for executing a controlled turn.
The restoring force generated by the Telemark binding while lifting the heel stems from the tensile force in a cable normally used to fix the ski boot in place in the binding, which increases as the heel lifts. This force arises due to the kinematic arrangement of the toe box, cable and heel relative to each other as the boot is kinked by lifting the heel. Herein, however, it turns out that the restoring force generated by the Telemark binding is not ideal, or at least not for all applications. Unfortunately, however, the restoring force or torque generated by the binding cannot be preset as desired in such cable-based bindings. One limiting factor here is that the cable also serves to fix the boot in place in the binding. This means that the tensile force in the cable can at no point be too low. On the other hand, too high a tensile force in the cable causes the boot to be too rigidly fixed in the binding, which then makes it harder to release the boot from the binding in the event of a fall. In this regard, it is particularly problematical that the tensile force in the cable is greatest when the heel is lifted the furthest, i.e., when the knee is bent the most. Studies in sports medicine have shown that susceptibility to ligament injuries is especially high in falls where the knee is bent. However, it is precisely in this injury-prone position that the conventional cable-based Telemark binding usually has the highest release resistance.
Due to this observed safety deficiency, it has been proposed that Telemark bindings be entirely mounted on a release plate, which is released when excessive loads are placed on the ski, similarly to the rotatory safety release of the boot known for alpine ski bindings. In this case, the separation between the ski and skier does not take place between the boot and binding given a safety release, however, but rather inside of the binding, so that part of the binding remains on the boot. This results in a comparatively complicated structural design and cumbersome handling.
As evident from the above description, Telemark bindings and alpine ski tour bindings currently differ fundamentally in their construction, so that structural details from one can hardly be applied to the other, and even less so are shared components used in the disparate binding types, which would be advantageous in the eyes of a manufacturer having both binding types in its product line. There are also no known ski bindings for which the alpine mode and Telemark mode would be options for a downhill run. For the comparatively high number of skiers familiar with alpine downhill runs, this raises the inhibition threshold when it comes to trying the Telemark style, since a complete second set of equipment is required for this purpose. A trained alpine skier with little Telemark experience will often hesitate to stray from the piste wearing exclusively Telemark equipment, fearing that he or she might be unable to master difficult passages in the Telemark style. The ability to switch from the Telemark mode to the alpine downhill mode as needed would tangibly diminish any reservations about enlisting the far less common Telemark technology.